This invention relates to a tool coupling of the kind that comprises a holder and an adapter for at least one cutting machining element, said adapter including a first serration intended to co-operate with a second serration of the holder, more precisely by bringing the serrations to engage each other by means of a clamping means while providing a torque resistant connection between the adapter and the holder. More specifically, the present tool is intended for parting and grooving operations.
Within the field of chip removing machining there are tool couplings of the general kind defined above for use in several different applications, however, usually in turning tools of different type. Thus under the trade name COROMANT CAPTO.sup.a (Manufacturer: Sandvik AB, Sweden) boring bars are marketed, said boring bars having such couplings. The holder constitutes for instance a bar for a cutting head mountable in a multi-purpose lathe, said cutting head having one or more machining elements in the shape of exchangeable inserts. In connection with previously known boring bars of this kind a first serration is provided at an essentially planar inner end surface of the cutting head, while a co-operating second serration is provided at an external or free end surface of the bar. In order to bring the serrations into engagement with each other several loose screws are used as clamping means, said screws having an enlarged head and being tightened in axial threaded holes that open in the serrated surface of the free end of the bar. More precisely, in this end surface of the bar, four equidistant separated holes are recessed, of which both of the two upper holes receive screws that are inserted through holes formed in the cutting head, and one or the other of the two lower holes receives a screw, depending on whether the cutting head in question is of a left-hand type or a right-hand type.
By the presence of the above-mentioned serrations in the two end surfaces of the bar and the cutting head respectively, said serrations being urged against each other, a very reliable, torque resistant connection is achieved between the bar and the cutting head. This in turn guarantees that the active insert is given and maintains a correct position. However, a disadvantage in connection with the previously known tool coupling is that the exchange of the cutting head is complicated and time-consuming. Thus, not less than three screws must initially be loosened and then again tightened to complete a tool exchange, which might take several minutes. The tool exchanges become especially difficult in such cases when the screws are hard to reach and/or have chips, dirt, grease deposits or the like in their key recesses. Under such circumstances the operational shutdowns for tool exchanges may be very time-consuming and expensive. Further, there is a risk that screws are lost since they must be loosened completely in order to allow dismounting of the cutting head.
A tool coupling using co-operating serrations in combination with screws such as clamping means in parting tools is disclosed in Swedish Patent Application No. 7813038-2. In this case the number of screws for clamping the adapter and the holder is three. This means that the activity of first disengaging three comparatively long screws and subsequently tightening them again when insert change is needed for indexing a new cutting edge, is very time consuming. Further, there is a risk that screws become lost since they must be loosened completely.